Key facts

  • Coding-decoding questions test rule consistency: the same operation must explain the given code and the asked code.
  • Letter codes use alphabet position, forward shift, backward shift, reverse alphabet pairing, rearrangement or alternate movement.
  • Number codes can use A = 1 to Z = 26, digit sums, products, differences, squares, reversal or paired first-last positions.
  • Symbol codes replace words, letters, relations or operations with signs, but each sign must keep one fixed meaning inside that question.
  • Blood-relation questions should be converted into a family tree with generation, gender, marriage and sibling links shown clearly.

Key Points at a Glance

  1. 1

    Coding-decoding questions test rule consistency: the same operation must explain the given code and the asked code.

  2. 2

    Letter codes use alphabet position, forward shift, backward shift, reverse alphabet pairing, rearrangement or alternate movement.

  3. 3

    Number codes can use A = 1 to Z = 26, digit sums, products, differences, squares, reversal or paired first-last positions.

  4. 4

    Symbol codes replace words, letters, relations or operations with signs, but each sign must keep one fixed meaning inside that question.

  5. 5

    Blood-relation questions should be converted into a family tree with generation, gender, marriage and sibling links shown clearly.

  6. 6

    Paternal means through the father and maternal means through the mother; this one word often decides uncle, aunt, cousin and grandparent relations.

  7. 7

    Negative clues such as "not daughter" or "not brother" do not prove the opposite unless the remaining possibilities are also ruled out.

  8. 8

    Sitting-arrangement questions require a fixed order or position map before options are checked.

  9. 9

    Practice questions should be solved by naming the rule first, applying it once, and checking that every clue still fits.

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What coding-decoding asks

Coding-decoding is a rule-finding question. The examiner gives one coded form and expects the candidate to infer how the original item was changed. In this CET Senior Secondary reasoning block, code and decode is an official syllabus item, so the safest preparation is to master short, repeatable rules rather than memorise examples. A code may move letters, reverse order, assign numbers, replace symbols, or combine two simple operations. The answer should never be chosen because it looks similar; it should be chosen because the same operation works on every part of the example.

Start by writing the evidence pair. If CAT is coded as FDW, compare C to F, A to D and T to W. Each letter moves 3 positions forward, so the rule is +3. The same rule gives DOG as GRJ. If JAIPUR is used as a Rajasthan-flavoured example, the city name is only a label; the proof still lies in letter movement and position.

Exam focus: coding questions reward a small table of original item, coded item and operation.

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